Solar panel with a translucent multi-walled sheet for heating a circulating fluid

ABSTRACT

A panel for generating electrical and thermal power comprises an upper layer formed by a translucent sheet having an array of photovoltaic cells and a support structure including a pair of multi-walled translucent sheets, and an underlying reflective sheet. The multi-walled translucent sheets each include a number of elongated channels, with the two sheets being arranged so that their channels lie perpendicular to one another for rigidity. The channels within at least one of the sheets are filled with circulating water, which is heated by solar energy not absorbed within the photovoltaic cells.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to solar panels and, more particularly, to solar panels producing both electrical and thermal energy.

2. Summary of the Background Art

A number of patents describe the use of photovoltaic cells to generate electricity, together with underlying circulating water to generate thermal energy. For example, U.S. Pat. No. 4,106,952 describes a solar panel including elements arranged generally in parallel planes that, starting from the top, include a transparent sheet, a plurality of converging lenses, a plurality of solar sells, an electrically insulating support plate, that, together with the sides of the solar unit and the top sheet form a vacuum chamber to reduce upward heat transfer by convection and conduction, a thermopile, a heat sink plate receiving heat from the thermopile, heat transfer fins receiving heat from the heat sink plate, and a serpentine conduit in heat exchange with the fins, which is used to heat water that may be used in the hot water system of a residence or for space heating purposes at a remote location.

U.S. Pat. No. 4,002,031 describes a solar energy converter using gallium arsenide photovoltaic cells to convert light to direct current, with the photovoltaic cells being thermally bonded to metallic heat exchangers through which a cooling fluid flows to remove heat energy that is not converted into electricity. The cooling fluid may be water, a liquid metal, or a vaporizable working fluid. After heating, this fluid is pumped through another heat exchanger to heat a working fluid of a heat engine, which is used to produce mechanical energy.

International Pub. No. WO 2004/099682 A2 describes a high-efficiency, small-scale, combined heat and power, concentrating solar energy system that is driven to track the sun along two axes. A power generation module includes a power conversion unit, such as a thermal engine or concentrated photovoltaic cells. A coolant, such as water, oil, or another fluid, such as a gas is circulated, reaching a temperature of. 120-180 degrees C., so that its heat can be used to drive an air conditioning system, as well as for space heating, etc.

U.S. Pat. No. 4,444,992 describes a photovoltaic-thermal solar cell including a semiconductor body having an antireflective top and bottom surfaces and coated on each of these surfaces with a patterned electrode covering less than 10 percent of the surface area. A thermal-absorbing surface is spaced apart from the bottom surface of the semiconductor, and a heat-exchange fluid is passed between the bottom surface and the heat-absorbing surface.

Other patents, such as U.S. Pat. Nos. 5,296,045 and 5,620,530 describe back reflectors formed as textured layers on photovoltaic devices.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, a solar panel includes a first translucent thermoplastic multi-walled sheet, a first input manifold and a first output manifold. The first multi-walled sheet has a plurality of channels extending in a first direction between an input end and an output end, opposite the input end. The first input manifold is attached to extend over openings of the plurality of channels at the input end of the first multi-walled sheet, including an input port and an input cavity connecting the input port with at least one of the openings of the plurality of channels at the input end of the first multi-walled sheet. The first output manifold is attached to extend over openings of the plurality of channels at the input end of the first multi-walled sheet, including an output port and an output cavity connecting the output port with at least one of the openings of the plurality of channels at the output end of the first multi-walled sheet. In this way, the input cavity is connected to the output cavity through the channels within the first multi-walled sheet.

The solar panel may additionally include a plurality of input end cavities and a plurality of output end cavities, with each of the input end cavities connects a plurality of the channels within the first multi-walled sheet at the input end of the first multi-walled sheet, and with each of the output end cavities connects a plurality of the channels within the first multi-walled sheet at the output end of the first multi-walled sheet. Such output end cavities are staggered among the channels within the first multi-walled sheet relative to the input end cavities, so that channels within the first multi-walled sheet connected to one another by one of the input end channels are connected to a pair of adjacent output end cavities, and so that channels within the first multi-walled sheet connected to one another by one of the output end channels are connected to a pair of adjacent input end cavities. The input cavity then connects the input port with at least one channel within the first multi-walled sheet not connected to another channel within the first multi-walled sheet by an input end cavity, and the output cavity then connects the output port with at least one channel within the first multi-walled sheet not connected to another channel within the first multi-walled sheet by an output end cavity. Such input end cavities and output end cavities may be disposed within the first multi-walled sheet or within the input and output manifolds.

Instead of including the input and output end cavities as described above, the solar panel may have a number of channels directly connected to both the input cavity of the input manifold and the output cavity of the output manifold.

Preferably, the solar panel additionally includes an array of photovoltaic cells above the first multi-walled sheet and a reflector disposed below the first multi-walled sheet. The solar panel may additionally include a second multi-walled sheet having channels extending perpendicularly to the channels within the first multi-walled sheet. These channels of the second multi-walled sheet may additionally be filled with a fluid, or the second multi-walled sheet may be used only to provide strength and rigidity within the solar panel.

The solar panel may additionally include frameworks spacing the photovoltaic array and the reflector away from the first and second multi-walled sheets to reduce the conduction-of heat away from the circulating fluid. An additional multi-walled sheet may be provided beneath the reflector for stiffness and for additional thermal insulation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a fragmentary longitudinal cross-sectional view of a solar panel built in accordance with a first embodiment of the present invention;

FIG. 2 is a block diagram of a system including the solar panel of FIG. 1;

FIG. 3 is a cross-sectional plan view of a first version of a heat exchanger for use within the solar panel of FIG. 1;

FIG. 4 is a fragmentary plan view showing a corner of the heat exchanger of FIG. 3;

FIG. 5 is a fragmentary plan view showing a corner of a photovoltaic array of the solar panel of FIG. 1;

FIG. 6 is a fragmentary cross-sectional plan view of second version of a heat exchanger for use within the solar panel of FIG. 1;

FIG. 7 is a cross-sectional plan view of a third version of a heat exchanger for use within the solar panel of FIG. 1;

FIG. 8 is a fragmentary longitudinal cross-sectional view of a solar panel built in accordance with a second embodiment of the invention;

FIG. 9 is a fragmentary longitudinal cross sectional view showing an edge portion of the solar panel of FIG. 8;

FIG. 10 is a fragmentary transverse cross-sectional view showing an edge portion of the solar panel of FIG. 8;

FIG. 11 is a side elevation of a solar panel built in accordance with the invention attached to a framework; and

FIG. 12 is a side elevation of a solar panel built in accordance with the invention attached to the roof of a structure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a fragmentary longitudinal cross-sectional view of a solar panel 10 built in accordance with a first embodiment of the present invention to include a first multi-walled sheet 12, a second multi-walled sheet 14, a reflector 16, and an array 18 of photovoltaic cells 20. The photovoltaic array 18 is disposed upwardly, in the direction of arrow 22, from the first multi-walled sheet 12, while the second multi-walled sheet 14 is disposed downwardly, opposite the direction of arrow 22, from the first multi-walled sheet 12, and the reflector 16 is disposed downwardly from the second multi-walled sheet 14.

Each of the multi-walled sheets 12, 14 is composed of a translucent thermoplastic resin, such as polycarbonate, having a number of parallel channels 24. Sheets of this type are available for architectural uses, such as the roofs and walls of greenhouses. For example, multi-walled translucent polycarbonate sheet material of this kind is available as VEROLITE TWINWALL Polycarbonate Sheeting from General Electric. Alternatively, polycarbonate multi-wall sheet material is available from POLYGAL Plastics Industries, Ltd. Ramat Hoshofet, Israel. For example, the channels 24 within the second multi-walled sheet 14 extend through the sheet 14 in-the direction of arrow 26. Since a sheet of this type is particularly rigid in the direction in which the channels 24 extend, the multi-walled sheets 12, 14 are arranged within the solar panel 10 so that their channels 24 extend in directions perpendicular to one another. In this way, rigidity is achieved in the direction of arrow 26 and also perpendicular thereto.

The photovoltaic cells 20 are translucent, and are mounted on a sheet 28 of translucent material, so that a portion of the solar energy striking the photovoltaic cells 20 that is not used in the generation of electricity proceeds through the translucent multi-walled sheets 12, 14 to be reflected off an upwardly directed reflective surface 30 of the reflector 16, so that at least a portion of the energy passes upward through the multi-walled sheets 12, 14 and the photovoltaic cells 20.

In accordance with the invention, the channels 24 within at least one of the multi-walled sheets 12, 13 are filled with a flowing fluid, such as water, that is heated by solar energy passing through the sheet 12, 13 and the fluid. The channels 24 within the other multi-walled sheet 12, 14 may be similarly filled with a flowing fluid, or the other multi-walled sheet 12, 14 may be provided simply for its contribution to the strength and rigidity of the solar panel 10, without its channels 24 being filled with a flowing fluid.

FIG. 2 is a block diagram of a system 26 including the solar panel 10, together with a pump 28 circulating a fluid through a first heat exchanger 30, including, for example, the first multi-walled sheet 12, and a second heat exchanger 32, including, for example the second multi-walled sheet 14. Radiant energy from the sun, represented by an arrow 34, travels through the photovoltaic array 18 and through both of the heat exchangers 30, 32 being then reflected by the reflector 16, so that at least a portion of this energy returns through the heat exchangers 30, 32 and the photovoltaic array 18. The passage of this radiant energy through the photovoltaic array 18 causes electricity to be generated, driving an electrical load 36. The passage of this radiant energy through the heat exchangers 30, 32 causes the fluid circulated by the pump 28 to be heated, with this fluid in turn heating a thermal load 38.

FIG. 3 is a cross-sectional view of a first version of the heat exchanger 30 for use within the solar panel 10. The heat exchanger 30 includes the multi-walled sheet 12, an input manifold 40 attached to extend over openings in channels 24 within the multi-walled sheet 12 at an input end 42 of the sheet 12, and an output manifold 44 attached to extend over openings in the channels 24 at an output end 46 of the sheet 12. The input manifold 40 includes an input cavity 48 connecting an input port 50 with the openings of channels 52 at the input end 42 of the sheet 12. The output manifold 44 includes an output cavity 54 connecting an output port 56 with the openings of channels 58 at the output end 46 of the sheet 12. Preferably, joints 55 between the sheet 12 and the manifolds 40, 42 are provided with a sealing compound or gaskets to prevent fluid leakage. For example, silicone sealants known to be compatible with the polycarbonate material of the multi-walled sheet 12 include SILGLAZE N GESIL N, from General Electric Co., Waterford, N.Y., and #999-A with 1205 Primer, from Dow Corning Corp., Midland, Mich.

The heat exchanger 30 additionally includes a number of input end cavities 60, each of which connects a plurality of the channels 24 with one another at the input end 42 of the sheet 12, and a number of output end cavities 62, each of which connects a plurality of the channels 24 with out another at the output end 46 of the sheet 12. The output end cavities 62 and the input end cavities 60 are staggered among the channels 24, being displaced so that channels 24 connected to one another by a single input end cavity 60 are connected to two adjacent output end cavities 62 and so that channels 24 connected to one another by a single output end cavity 62 are connected to two adjacent input end cavities 60. In this way, fluid being pumped through the heat exchanger 30 is constrained to follow a serpentine path through the sheet 12, remaining within the sheet for a relatively long time to be heated by radiation passing trough the sheet 12.

In the example of FIG. 3, the input end cavities 60 are formed by spaces between an interior surface 64 of the input manifold 40 and the ends of walls 66 between adjacent channels 24, with adjacent input end cavities 60 being separated from one another by walls 68 extending to the interior surface 64. Similarly, the output end cavities 62 are formed by spaces between an interior surface 70 of the output manifold 44 and the ends of walls 72 between adjacent channels 24, with adjacent output end cavities 62 being separated from one another by walls 74 extending to the interior surface 70. While the input end cavities 60 and the output end cavities 64 each connect four adjacent channels 24, so that the fluid flows through two adjacent channels 24 in the same direction, it is understood that alternately a greater number of channels or as few as two channels can be connected this way to produce different patterns of fluid flow.

In the example of FIG. 2, the output port 56 of the first heat exchanger 30 is show n as being connected to the input port 50 of the second heat exchanger 32 by a tube 76, with additional piping 78 connecting the heat exchangers 30, 32 to the thermal load 38 and the pump 28. It is understood that alternatively, may be connected to the output port 56 of the first heat exchanger 30, as well as to its input port 50, so that fluid flows through the first heat exchanger 32, with the second heat exchanger 32 being eliminated in an alternative configuration.

FIG. 4 is a fragmentary plan view showing a corner of the heat exchanger 30, which includes a channel member 80 extending along and around an edge portion 82 of the multi-walled sheet 12, being fastened to the input manifold 40 by screws 84. As shown in FIG. 3, channels 86 within the sheet 12, but under the channel member 80, are not connected to the fluid flow. Preferably, the channel member 80 extends along the edge 82 to be similarly connected to the output manifold 44, with a similar channel member 84 extending along an opposite edge 86 of the sheet 12.

FIG. 5 is a fragmentary plan view showing a corner of the photovoltaic array 18, in which individual photovoltaic cells 20 are attached to a translucent sheet 28. The photovoltaic array 18 additionally includes a number of conductors 86 connected to one another and, as shown in FIG. 2, by electrical lines 88 to the electrical load 36. Photovoltaic cells suitable for such use are widely available from a number of manufacturers. For example, photovoltaic cells sold as E6+Solar Cells from ErSol® Solar Energy AG of Erfurt, Germany may be used.

FIG. 6 is a fragmentary cross-sectional plan view of a second version 90 of a heat exchanger for use within the solar panel 10. This heat exchanger 90 includes a number of input end cavities 92 connecting channels 94 within a multi-walled sheet 96 in the manner of input end cavities 60, as described above in reference to FIG. 3. However, the walls 98 separating the channels 94 all extend to the input end 100 of the sheet 96, with the input end cavities 92 being formed within an input manifold 102. The input end cavities 92 are separated from one another by walls 104 formed within the input manifold 102. Preferably, the heat exchanger 90 also includes at an output end (not shown) a similarly configured output manifold (not shown) in which output cavities are formed, with the output cavities being staggered relative to the input cavities in the manner described above in reference to FIG. 3.

FIG. 7 is a cross-sectional plan view of a third version 106 of a heat exchanger for use within the solar panel 10. This heat exchanger 106 includes an input manifold 108 having an input cavity 110 and an output manifold 112 having an output cavity 114, with both the input cavity 112 and the output cavity 114 covering openings of all the channels 116 in a multi-walled sheet 118, so that all the channels 116 are directly connected to both the input cavity 112 and the output cavity 114. Thus, the flow of a fluid through the sheet 118 proceeds directly in a single direction, without following a serpentine pattern as described above in reference to FIG. 3.

FIG. 8 is a fragmentary longitudinal cross-sectional view of a solar panel 120 built in accordance with a second embodiment of the invention. Like the solar panel 10, previously discussed in reference to FIG. 1, the solar panel 120 includes a photovoltaic array 18, a reflector 16, a first multi-walled sheet 12 and a second multi-walled sheet 14, with one or both of these sheets 12, 14 forming a portion of a heat exchanger, for example, as described above in reference to FIGS. 2-7. Since various aspects of these elements are as described above, they are accorded like reference numbers.

The solar panel 120 additionally includes an upper framework 122 holding the photovoltaic array 18 in a spaced-apart relationship with the first multi-walled sheet 12 and a lower framework 124 holding the reflector 16 in a spaced-apart relationship with the second multi-walled sheet. In this way, air spaces are formed to reduce conductive and convective heat loss between the heated fluid within either or both the sheets 12, 14 and the elements exposed to ambient conditions outside the solar panel 120. Additionally, a third multi-walled sheet 126 is provided to support the reflector 16 and to provide additional thermal insulation.

FIG. 9 is a fragmentary longitudinal cross-sectional view showing an edge portion-of the solar panel 120. An input manifold 128 is shown as including an input cavity 130 connected to a channel 132 within the second multi-walled sheet 14.

FIG. 10 is a fragmentary transverse cross-sectional view showing another edge portion of the solar panel 120. An input manifold 134 is shown as including an input cavity 136 connected to a channel 138 within the first multi-walled sheet 12.

The input manifolds 128, 134 are attached to one another by means of a number of screws 140 extending through holes 142 in the manifolds 128, 134 and through a pair of brackets 144 disposed above and below the manifolds 128, 134. Similarly, the solar panel 120 includes a pair of output manifolds (not shown) extending to a corner opposite the corner having components that are visible in FIGS. 9 and 10. These output manifolds are attached to one another and to the input manifolds by screws and brackets (not shown) that are similar or identical to the screws 140 and brackets 144 shown in FIGS. 9 and 10.

In the example of FIGS. 9 and 10, the upper framework 122 and the lower framework 124 each include frame members 146 extending along all four edges of the multi-walled sheets 12, 14. In addition, tie rods 148 are includes to facilitate the assembly of the solar panel 120. Alternately additional frame members (not shown) may be applied to increase stiffness of a central portion of a solar panel built in a large size, or the solar panel may the built with frame members extending along a first pair of opposite sides and with tie bars extending along the other pair of opposite sides.

FIG. 11 is a side elevation of a solar panel 150 attached to a support framework 152 in a freestanding application. As described above in reference to FIG, 2, fluid is circulated through the solar panel 150 by means of pipes 88, together with a tube 76. The solar panel 150 is preferably arranged at an angle aligning it to be perpendicular to an average direction of radiation from the sun, with the upward and downward directions described above in reference to arrow 22 being established as perpendicular to the surface 154 of the solar panel 150. The framework 152 may be provided with adjustable attachment devices for establishing the angle at which the solar panel 150 is held or for changing this angle to compensate for variations in the angle of inclination of the sun during a year.

FIG. 12 is a side elevation of a solar panel 156, such as the solar panel 10 or the solar panel 120, built in accordance with the invention, attached to a roof 158 of a structure 160.

While the invention has been described in its preferred forms or embodiments with some degree of particularity, it is understood that this description has been given only by way of example, and that many variations can be made without departing from the spirit and scope of the invention, as defined in the appended claims. 

1. A solar panel comprising: a first translucent thermoplastic multi-walled sheet having a plurality of channels extending in a first direction between an input end and an output end, opposite the input end; and a first input manifold attached to extend over openings of the plurality of channels at the input end of the first multi-walled sheet, including an input port and an input cavity connecting the input port with at least one of the openings of the plurality of channels at the input end of the first multi-walled sheet; a first output manifold attached to extend over openings of the plurality of channels at the input end of the first multi-walled sheet, including an output port and an output cavity connecting the output port with at least one of the openings of the plurality of channels at the output end of the first multi-walled sheet, wherein the input cavity is connected to the output cavity through the channels within the first multi-walled sheet.
 2. The solar panel of claim 1, additionally comprising an array of photovoltaic cells upwardly disposed from the first multi-walled sheet.
 3. The solar panel of claim 2, additionally comprising a reflector downwardly disposed from the first multi-walled sheet, wherein the reflector includes an upwardly facing reflective surface.
 4. The solar panel of claim 1 additionally comprising a reflector downwardly disposed from the first multi-walled translucent thermoplastic sheet, wherein the reflector includes an upwardly facing reflective surface.
 5. The solar panel of claim 1, additionally comprising a plurality of input end cavities and a plurality of output end cavities, wherein each of the input end cavities connects a plurality of the channels within the first multi-walled sheet at the input end of the first multi-walled sheet, each of the output end cavities connects a plurality of the channels within the first multi-walled sheet at the output end of the first multi-walled sheet, the output end cavities are staggered among the channels within the first multi-walled sheet relative to the input end cavities, so that channels within the first multi-walled sheet connected to one another by one of the input end channels are connected to a pair of adjacent output end cavities, and so that channels within the first multi-walled sheet connected to one another by one of the output end channels are connected to a pair of adjacent input end cavities, the input cavity connects the input port with at least one channel within the first multi-walled sheet not connected to another channel within the first multi-walled sheet by an input end cavity, and the output cavity connects the output port with at least one channel within the first multi-walled sheet not connected to another channel within the first multi-walled sheet by an output end cavity.
 6. The solar panel of claim 5, wherein the input end cavities and output end cavities are disposed within the first multi-walled sheet.
 7. The solar panel of claim 5, wherein the input end cavities are disposed within the input manifold, and the output end cavities are disposed within the output end manifold.
 8. The solar panel of claim 1, wherein a plurality of the channels within the first multi-walled sheet are directly connected to both the input cavity and the output cavity.
 9. The solar panel of claim 1, additionally comprising a second translucent thermoplastic multi-walled sheet having a plurality of channels extending in a direction perpendicular to the first direction between an input end and an output end, opposite the input end, wherein the second multi-walled is disposed below the first multi-walled sheet.
 10. The solar panel of claim 9, additionally comprising a reflector having a surface facing upward and disposed below the second multi-walled sheet.
 12. The solar panel of claim 10, additionally comprising a framework holding the reflector in a spaced-apart relationship with the second multi-walled sheet.
 13. The solar panel of claim 9, additionally comprising a third translucent thermoplastic multi-walled sheet having a plurality of channels extending between an input end and an output end, opposite the input end, wherein the third multi-walled is disposed below the reflector.
 14. The solar panel of claim 10, additionally comprising an array of photovoltaic cells upwardly disposed from the first multi-walled sheet.
 15. The solar panel of claim 13, additionally comprising a framework holding the array of photovoltaic cells in a spaced-apart relationship with the first multi-walled sheet.
 16. The solar panel of claim 9, additionally comprising: a second input manifold attached to extend over openings of the plurality of channels at the input end of the second multi-walled sheet, including an input port and an input cavity connecting the input port with at least one of the openings of the plurality of channels at the input end of the second multi-walled sheet; a second output manifold attached to extend over openings of the plurality of channels at the input end of the second multi-walled sheet, including an output port and an output cavity connecting the output port with at least one of the openings of the plurality of channels at the output end of the second multi-walled sheet, wherein the input cavity is connected to the output cavity through the channels within the second multi-walled sheet.
 17. The solar panel of claim 15, additionally comprising a plurality of first input end cavities, a plurality of first output end cavities, a plurality of second input end cavities, and a plurality of second output end cavities, wherein each of the first input end cavities connects a plurality of the channels within the first multi-walled sheet at the input end of the first multi-walled sheet, each of the first output end cavities connects a plurality of the channels within the first multi-walled sheet at the output end of the first multi-walled sheet, the first output end cavities are staggered among the channels within the first multi-walled sheet relative to the first input end cavities, so that channels within the first multi-walled sheet connected to one another by one of the first input end channels are connected to a pair of adjacent first output end cavities, and so that channels within the first multi-walled sheet connected to one another by one of the first output end channels are connected to a pair of adjacent first input end cavities, the input cavity within the first input manifold connects the input port with at least one channel within the first multi-walled sheet not connected to another channel within the first multi-walled sheet by an input end cavity, the output cavity within the first output manifold connects the output port with at least one channel within the first multi-walled sheet not connected to another channel within the first multi-walled sheet by an output end cavity, each of the second input end cavities connects a plurality of the channels within the second multi-walled sheet at the input end of the second multi-walled sheet, each of the second output end cavities connects a plurality of the channels within the second multi-walled sheet at the output end of the second multi-walled sheet, the second output end cavities are staggered among the channels within the second multi-walled sheet relative to the second input end cavities, so that channels within the second multi-walled sheet connected to one another by one of the second input end channels are connected to a pair of adjacent second output end cavities, and so that channels within the second multi-walled sheet connected to one another by one of the second output end channels are connected to a pair of adjacent second input end cavities, the input cavity within the second input manifold connects the input port with at least one channel within the second multi-walled sheet not connected to another channel within the second multi-walled sheet by an input end cavity, and the output cavity within the second output manifold connects the output port with at least one channel within the second multi-walled sheet not connected to another channel within the second multi-walled sheet by an output end cavity.
 18. The solar panel of claim 16, additionally comprising a tube connecting the output port of the first output manifold with the input port of the second input manifold. 